Invasive Fish and Sea Urchins Drive the Status of Canopy Forming Macroalgae in the Eastern Mediterranean

• Published in: Biology (Basel, Switzerland) Vol. 12; no. 6; p. 763
• Main Authors: Nikolaou, Athanasios, Tsirintanis, Konstantinos, Rilov, Gil, Katsanevakis, Stelios
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 24-05-2023; MDPI
• Subjects: Algae; Biodiversity; Biomass; canopy-forming macroalgae; Climate change; Coastal zone; Conservation; Cystoseira; Cystoseira sensu lato; Echinoidea; Ecosystems; Food chains; Forests; Grazing; herbivory; invasive species; marine forests; Productivity; Spatial heterogeneity; tropicalization; Vertical distribution; Greece; Aegean Sea; Netherlands; Israel; Cyprus; Mediterranean Sea; Crete; Skyros; canopy-forming macroalgae; herbivory; tropicalization; marine forests; Cystoseira sensu lato; invasive species
• ISSN: 2079-7737; 2079-7737
• DOI: 10.3390/biology12060763

Canopy-forming macroalgae, such as
, increase the three-dimensional complexity and spatial heterogeneity of rocky reefs, enhancing biodiversity and productivity in coastal areas. Extensive loss of canopy algae has been recorded in recent decades throughout the Mediterranean Sea due to various anthropogenic pressures. In this study, we assessed the biomass of fish assemblages, sea urchin density, and the vertical distribution of macroalgal communities in the Aegean and Levantine Seas. The herbivore fish biomass was significantly higher in the South Aegean and Levantine compared to the North Aegean. Very low sea urchin densities suggest local collapses in the South Aegean and the Levantine. In most sites in the South Aegean and the Levantine, the ecological status of macroalgal communities was low or very low at depths deeper than 2 m, with limited or no canopy algae. In many sites, canopy algae were restricted to a very narrow, shallow zone, where grazing pressure may be limited due to harsh hydrodynamic conditions. Using Generalized Linear Mixed Models, we demonstrated that the presence of canopy algae is negatively correlated with the biomass of the invasive
spp. and sea urchins. The loss of
forests is alarming, and urgent conservation actions are needed.